Study On The Mechanism Of Excessive Stress Mediating Intervertebral Disc Degeneration And Low Back Pain In Mice By Up-Regulating The Expression Of Bdnf In Cartilage Endplate

Background:Cartilage endplate degeneration is the main risk factor for intervertebral disc degeneration,and the nerve ingrowth is an important pathological basis for low back pain.The inflammatory microenvironment is an important factor that promotes nerve growth,and inhibiting inflammation and nerve growth is an important strategy for the treatment of intervertebral disc degeneration and low back pain.Brain Derived Nerve Factor(BDNF),as the most abundant neurotrophic factor in the human body,exhibits pro-inflammatory effects in peripheral tissues and plays an important role in promoting nerve growth and maintaining pain.Previous studies have shown that the expression of BDNF in the intervertebral disc is positively correlated with the degree of degeneration,which may play an important role in low back pain.However,the role of BDNF in cartilage endplate inflammation and the effect of anti-BDNF therapy on low back pain are still unclear.Cartilage endplate is an important tissue that bears mechanical stress,and excessive stress often leads to damage and degeneration of cartilage endplate.Studies have shown that in the nervous system,mechanical stress stimulation can affect the signaling pathway that regulates the expression of BDNF.However,the research on the mechanism of BDNF regulation by mechanical stress stimulation has not been perfected,and the related research in cartilage endplate has not been reported yet.Objective:To explore the role and mechanism of excessive stress up-regulating the expression of BDNF in cartilage endplates and promoting low back pain due to intervertebral disc degeneration,and to explore the molecular mechanism of excessive stress regulating BDNF.Method:Animal experiments:A mouse model of lumbar instability combined with a bipedal standing model was constructed,and 24 10-week-old C57BL/6 mices were selected and divided into control group,model group,blank group(intraperitoneal injection of normal saline),Rescue group(intraperitoneal injection of BDNF receptor inhibitor,0.5mg/kg).In each group,the degree of low back pain was evaluated by low back pain-related behavioral experiments(hot plate,Von Frey,open field,etc.)at 0,8,and 12 weeks after modeling.Histological staining(Red O fast green staining,immunohistochemistry)to detect the degree of degeneration of intervertebral disc and cartilage endplate(MMP-13,Collagen X),inflammatory factors(IL-1β,TNF-α),BDNF/TrkB expression in mice in each group and nerve growth profile(CGRP).Cell experiment:Isolate intervertebral disc cartilage endplate cells,act on the cells through the FX-5000T stretching system(20%amplitude,0.1 Hz)to simulate mechanical stress stimulation,add BDNF receptor inhibitor ANA-12,and then add Ca2+ chelate respectively mixture BATPA,CaMKII inhibitor KN93 and NMDAR inhibitor Ro 25-6981 were used to detect the expression of inflammatory factors,pain factors,NMDAR/CaMKII/CREB signaling pathway and BDNF/TrkB in the cells by ELISA and Western Blot experiments,and culture SH-SY5Y Cells to assess the regulation of neuronal growth by chondrocyte secretions.Results:Animal experiment:The behavioral evaluation showed that compared with the control group,the behavioral changes related to low back pain in the model mice were significant,the sensitivity of thermal pain,cold pain,central axis pain and mechanical pain was significantly increased,and the activity ability and willingness were decreased.Inhibition of BDNF/TkB signal pathway could significantly improve the above changes.The histological results showed that compared with the control group,the degeneration of the cartilage endplate of the intervertebral disc in the model mice was significantly accelerated,and the positive cell rates of IL-1β,TNF-α,BDNF,and TrkB in the cartilage endplate were significantly increased,and inhibiting the BDNF/TrkB signaling pathway can inhibit nerve growth.The results of cell experiments showed that mechanical stress stimulation could significantly promote the abnormal inflammatory reaction of endplate chondrocytes,its secretion could promote the growth of nerve cells,and inhibition of BDNF/TkB expression could reverse the above changes.Blocking the NMDAR/CaMKII/CREB signal pathway can inhibit the promotion of mechanical stress stimulation on the expression of BDNF/TRkB in cartilage endplate cells.Conclusion:Excessive stress can promote the expression of BDNF in the cartilage endplate of the intervertebral disc and the formation of an inflammatory environment through the NMDAR/CaMKII/CREB signaling pathway,and mediate the degeneration of the intervertebral disc and the occurrence of low back pain.